Mortar sight



G. L. HERTER MORTAR SIGHT July 17, 1951 Filed June 11, 1947 3 Sheets-Sheet l gvvuc/Mm EEEIREEL HERTER,

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Skim/mm G. L. HERTER MORTAR SIGHT July 17, 1951 3 SheetsSheet 2 Filed June 11, 1947 :1 I M) onto L G. L. HERTER July 17, 1951 MORTAR SIGHT 3 Sheets-Sheet 5 Filed June 11, 1947 Patented July 17, 1951 a it SEARQ UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

In all types of mortar sights in use at the present time, the collimator is rotatable about a normally horizontal axis through the complete useful range of mortar elevations. That is, the line of sight of the collimator may be depressed relatively to the bore axis of the mortar through angles of, say, from 40 to 90, so that when the mortar and sight are elevated as a unit to restore the collimator to the target, the mortar is elevated by the corresponding amount.

In some of these types of sights, however, while otherwise very satisfactory, the sight is rotatable about a vertical axis through a limited range movement only, say, 150 mils (about 85) on each side of the vertical plane through the mortar barrel. This limited range of movement limits the usefulness of the sight in actual combat because it cannot be used in indirect fire unless the aiming point is within 150 mils or either side of the actual target. However, such a limitation often renders the use of the sight impossible or highly dangerous to the mortar crew because it must be used without substantial shelter between the crew and enemy fire. As a result, such sights are often ignored altogether by the mortar crew and firing is conducted on a blind hit or miss basis.

It is therefore the general purpose of my invention to avoid the aforesaid drawbacks inherent in the type of mortar sight just described, by providing a construction whereby the collimator may be rotated 640G mils in azimuth to the nearest mil, so that indirect fire may be conducted by sighting on an aiming point well to the rear of the mortar, whereby the mortar crew may have ample protection between the mortar and the enemy.

A further object is to provide a device in the nature of an attachment that may be quickly applied to existing mortar sights without structural changes in the sights and with the removal of but a single bolt.

Another object is to provide a mortar sight that may have an azimuth adjustment through 360, in. steps of 100 mils, with a fine adjustment to the nearest mil between the aforesaid steps.

A. still further object is to provide a mortar sight adjustable in course steps as in the proceeding paragraph, merely by an axial thrust or pull, coupled with a turning movement, whereby adjustment may be efiected quickly and easily with one hand.

A further object is to provide a mortar sight 2 that is highly accurate, efiicient, and that may be collapsed into a minimum of space when detached from the mortar or when not in use and attached to the mortar.

Other objects and advantages of my invention will become apparent as the description proceeds.

In the drawings:

Figure 1 is a sectional elevation, taken upon a plane indicated by the line ll, Figure 2, of astandard Army mortar sight.

Figure 2 is an elevation, partly in section in a plane at right angles to the plane of Figure 1, and taken upon the line 22, Figure 1.

Figure 3 is a sectional elevation of an extension for use with the sight of Figures 1 and 2, and taken on the line 3-3, of Figure 4.

Figure 4 is an elevation of the extension of Figure 3, as seen in a plane at right angles to Figure 3, portions being shown in section on line 44, Figure 3.

Figure 5 shows a central section through the upper detent part, in a plane normal to the pivot axis of the collimator thereon.

Figure 6 is an elevation of the upper detent part of Figure 5, at right angles to the plane of Figure 5.

Figure 7 is a development of the azimuth mil scale extending about the detent part shown in Figures 5 and 6.

Figure 8 is a central vertical section through the lower detent part.

Figure 9 is an elevational view of a mortar sight, incorporating the 360 detent feature there- Figure 10 is a central vertical section of the sight of Figure 9, and taken upon a plane indicated by the line llll ll, of Figure 9.

Figure 11 is a horizontal section taken upon a plane indicated by the line HH, of Figure 9, and showing the fine azimuth adjustment feature.

Figure 12 is a section taken upon the line I2l2 of Figure 10, showing the elevation adjustment means.

Figure 13 is a modified form of deflection head showing also a collapsible collimator and mirror mounting.

Figure 14 is a detail view of the collimator bracket and the collimator carried thereby and looking from the right in Figure 13.

Referring in detail to the drawing, numeral l indicates a bracket having beveled guides surfaces 2 and 3 adapted to be received between undercut guides formed upon the mortar. A latch 4 is pivoted on bracket l, by means of a pivot pin 5 and is urged into counterclockwise rotation as viewed in Figure 2, by a spring 6 surrounding the pin. The latch 4 has a catch surface I lying in a plane between surface 2 and 3 which, as the bracket is slid downwardly between'the undercut guideways on the mortar, snaps under a coacting, downwardly, facing surface on the mortar'when the bracket is fully seated between the guideways. The sight is thus held firmly in position upon the mortar, but may be quickly released by pressing on surface 8 of latch 4.

Bracket I has a hub 9 turned thereon, undercut at its base as at ID to form a channel receiving a coil torsion spring II whose purpose will be subsequently described. A worm gear I2 fits hub 9 and is fixed against rotation thereon by a plurality of Woodruff keys I3. Axial displacement of the gear I2 is prevented by a screw I4 threaded into an axial bore in hub 9, and held against rotation by a locking screw I5.

The elevation head I6 has a bore journaled at one end upon a turned surface on bracket I, and at the other end upon gear I2. As shown upon Figure 2,.head. I6 has a bore forming a continuation of annular channel ID. The torsion spring II has one end engaging a slot in head l6 and the other engaging an aperture in bracket I. This spring is placed under tension in assembly so that it acts to urge head I6 into rotation on hub, 9 to thus take up any play between the teeth of gear I2 and a worm II, formed upon shaft I8. This shaft has a knob l9 attached to its end projecting from head IS. A micrometer scale 29 is carried by the knob and is readable against an indicator on head I6. This scale is divided into, 10 equal divisions, each subdivided into four parts. The gear ratio is such that one rotation of shaft I8, rotates head I6 through 10. A coarse scale is formed on surface 2| of head I6 and moves opposite an indicator, not shown, on hub 9. .This scale is graduated in units of 10, from 40 to 90. Thus, in conjunction with knob I9, the head I6 may be rotated through a maximum angle of 50 in minimum steps of minutes. A fore and aft level 23 as well as a cross level,32 are mounted in cylindrical cavities of housing I6, as clearly shown at Figure 2.

A deflection head 22 is pivoted on elevation head I6, for movement about a normally vertical axis defined by pivot screw 24. A coil torsion spring 25 is mounted within an annular channel in head I6, concentric of screw 24, and acts to urge head 22 into rotation. Head 22 carries a pin 26 having an extension 21 on one end, eccentric of its axis. The pin is fixed to head 22 by a screw 28. The extension 21 has a smooth fit between the threads of a worm 29. This worm is rotatable only upon the smooth portion of a screw 36, threaded into head I6 and having a head in engagement with a deflection knob 3|. As shown in Figure 2, this knob is graduated both ways from a zero position for left and right deflection. Thus, by turning knob 3|, worm 29 acts to deflect head 22 in a corre-- sponding direction, the parts being proportioned to afford a deflection of 100 mils in each direc tion from an initial position in which the line of sight of the collimator lies in a plane normal to the elevation axis of the mortar. Spring 25 is pre-tensioned to take up any back-lash or play throughout the range of rotation of head 22.

Deflection head 22 is formed with an upstanding, sector having an opening for the reception of a pivot bolt 33. The collimator 34 is pivoted on pin 33 by means of two depending space 4 semi-circular projections embracing the aforesaid sector upon respectively opposite sides thereof. The collimator includes a pair of superposed sights riveted to the aforesaid projections. The lower sight is open and consists merely of a notched projection 35 at the rear end, cooperating with a vertical wire 36 at the other end. The upper sight comprises a standard eyelens 31 and reticle 38 giving a low order of magnification.

The structure just described is well known and, while satisfactory under certain conditions of use, has the drawback that the limited deflection about the axis of screw 24, prevents its use where a relatively large azimuth angle exists between the target and a desired aiming point. To overcome the deflect noted, I have provided an extension shown at Figures 3 to 8, inclusive, and comprising a lower detent member 46 consisting generally of a cup-shaped or cylindrical portion 4I from which depend a pair of spaced parallel projections 42 and 43, having two pairs of aligned pivot holes 44 and 45 formed therethrough. As shown in Figure 8, portion 40 has an upstanding circular flange 46, apertured to receive a pivot screw 47 whose head slidably fits the inner cylindrical surface of the flange. The screw 41 is threaded into a central aperture of upper detent member 48 in the form of an inverted cup. As clearly shown, the two detent members have their meeting edges regularly notched or serrated in steps of 200 mils each. The serrated edges are yieldingly urged into engagement by a compression spring 49 acting between the head of screw 41 and the abutment on the upper edge of flange 46. A locking screw 50 holds screw 41 in assembled position. The upper detent member 48 has a scale 5I about its circumference, extending in opposite directions from a zero graduation. Graduation numerals are in hundreds of mils so that each scale extends throughout a semi-circumference, right and left, from 0 to 32. This scale is shown developed at Figure 7. As shown in Figures 3 and 4, a lever 52 is pivoted between projections 42 and 43, on a bolt 53 mounted in holes 45. One end of this lever abuts against the head of screw 41 while the other end extends outwardly to provide 'a manipulating portion which, when pressed, acts to axially translate member'48 and to separate the teeth of the two members. When this is done, member 48 and the parts carried thereby, may be rotated about the axis of screw 41 by means of knurled band 54.

Member 48 is formed with a pair of upstanding ears 55 and 56 having aligned holes 51. Channels 59 and 60 having arcuate bottoms concentric of holes '51, are formed as shown in Figures 3 and 4, 'each having one side flush with the outside surfaces of ears55 and 56, respectively. The spacing of such outside surfaces is equal to the thickness of the sector portion of deflection head 22, so that collimator 34 may be used, or a separate collimator 58 may be provided, similar in construction to 34. The construction is such that, when the collimator is in position on pivot bolt 6|, the arcuate edges of its spaced projections, fit the respective channels 59 and 60. The open and telescopic sights are indicated at 62 and 63, respectively, Figure 4.

In using the extension with a sight such as is shown at Figures 1 and 2, it is sufiicient merely to remove bolt 33 and place the extension so that its projections 42 and 43 embrace the sector of deflection head 22, then replace the bolt through holes 44. The square lower edges of the projections then lie snugly against the fiat upper surface of the deflection head and thereby prevent any tilting of the detent members on the deflection head. Collimator 58 may then be positioned to embrace ears 55 and 56 and bolt 51 inserted through the aligned holes, as shown at Figure 4. Alternatively, the collimator 34 may be used in place of 58, or any other collimator may be substituted having the necessary construction and projections. As shown upon Figure 4, the peripheral edges of ears on the collimator are received in the respective channels 59 and 60 to thereby form a compact construction.

After the sight has been attached by bracket I to the mortar, and a target has been selected, the leader determines the angular elevation of the mortar corresponding to the range of the selected target, as well as the azimuth angle in mils between the target and any selected aiming point, such as an easily visible tree or post. The mortar is leveled so that the bubble of cross level 32 is centered, directed in the general direction of the target, and knob I9 is turned to depress the sight until the coarse elevation scale on surface 2 I indicates the desired mortar elevation to the next lowest multiple of ten degrees. The adjustment is continued until scale 20 indicates the difference between the aforesaid desired elevation and the value previously indicated on the coarse elevation scale. The entire mortar and sight are now elevated until the bubble of level 23 is centered.

Next the upper detent member 48 is raised against the action of spring 49, by pressure upon the projecting end of lever '52, until the teeth of the two detent members are clear of each other. Upper member 48 is turned until the next lowest multiple of 200 mils below the desired angular setting is opposite the indicator line on member 4|. Both operations may be performed with one hand. The lever 52 is now released and deflection knob 3I is turned right or left, in accordance with the direction of the aiming point from the target, until its scale indicates the difference between the desired angle and that set on the detent members. For example if the desired angle is 645 mils, left, member 48 will be rotated through 600 mils left, relatively to M, and knob 3| will be rotated left, until its 45 mil graduation is opposite the indicator. The entire mortar and sight are traversed slightly in azimuth to align the sight upon the aiming point, the levels are checked and any necessary adjustments made to center them, while maintaining the line of sight on the aiming point. The mortar is then ready for firing. The actual operation requires but a few seconds-much less than the time required to explain it. As long as levels 23 and 32 are centralized, the collimator may be tilted through relatively small angles about the axis of bolt BI, so that the aiming point is not required to be in the exact horizontal plane of the sight. Thus it will be noted that the axis on which elevation head I6 is mounted, is normally horizontal, while the axis on which deflection head 22 is mounted on head I6, is normally vertical. The term normally as used in the claims thus means the position of the parts at the time the mortar is fired.

In Figures 9 to 12, inclusive, I have shown a second form of the invention wherein 64 is a bracket that may be similar in all respects to bracket I and carry a latch 65 operating in the same manner as latch 4, to secure the bracket in position on a mortar. Bracket 64 has an integral counterbored opening 68, and a worm housing 61 defining an axis generally tangential of opening 66. A hollow pivot screw 68 has a smooth shank fitting opening 66 and a head seated within the counterbore thereof. An elevation head 69 has an internally-threaded extension II which engages the threaded end of screw 68 and is fixed thereto by a set screw I0, whereby the head is pivotally mounted. Teeth I2 are formed over a portion of the periphery of extension I I, as shown upon Figure 12, and mesh with a worm I3 carried on a shaft I4. This shaft is journaled in housing 61 in the manner clearly shown upon Figure 12, and at its protruding end has a knob I5 secured thereto by a collar I6 and screw 11. A skirt I8 is clamped between the aforesaid collar and screw and overlaps the adjacent portion of housing 61. This skirt carries an elevation scale I03 cooperating with an indicator I9, Figure 9, on housing 81. A coarse scale is formed on a sector I04 fixed to bracket 64. This scale is graduated in steps of 100 mils over the desired range of elevation, and cooperates with an indicator mounted upon an arm I05 which is fixed to extension I I. Scale I04 is concentric of the axis of screw 68 and the two scales are so coordinated that that on skirt I8 is at zero, when the indicator mark on arm I05 is opposite any 100-mil graduation. Since scale I03 is graduated over a range of 100 mils for a complete turn, depression of the line of sight relatively to the mortar may be efi'ected to the nearest mil. A fore and aft level and a cross level 83', are mounted upon head 69.

The main portion of head 69 has a central bore receiving a bushing 8I. The upper end of said main portion is formed with regularly-spaced teeth 82, extending 360 about the axis of bushing 8|. The tooth spacing may conveniently be 200 mils right and left from initial or zero deflection position, as in the case of the species of Figures l-8. Bushing 8| is threaded at its upper end to receive a collar 83, fixed thereon, as by a screw 84. This collar has a lower surface formed with teeth 85 identical in spacing with teeth 82 and yieldingly held in engagement with teeth 82 by a coil spring 86 seated within a counterbore in head 69 and abutting at one end against the bottom of the counterbore and at the other end against a shoulder formed by nut 81 threaded upon the lower end of a shaft 88. This shaft is shown at Figure 10, as formed integrally with a deflection member 89 and it will be noted that the spring 88 acts to compress collar 83 between head-69 and deflection member 89.

The parts 83 and 89 coact to form an annular chamber at their contacting surfaces. A torsion coil spring 90 is located within the aforesaid chamber and has its ends bent at right angles to engage within holes in members 69 and 89, respectively. The spring is initially under tension to urge the aforesaid member 89 into clockwise rotation relatively to collar 83, as seen in Figure 11. A generally radial projection formed integrally with member 89 carries a screw 9I having a head formed as a portion of a sphere. The screw has a reduced smooth shank, adapted to be engaged by a set screw 92.

A second radial projection is formed integrally with collar 83 to provide the internally threaded hub 93 engaged by the shank portion 94 of a micrometer screw having a contact 95 and a barrel or skirt 96 having graduations about its periphery as shown in Figure 9. These graduations may conveniently be in units of two mils each, and extend through a range of 200 mils, correspond ing to a complete single rotation of skirt 9B. Thus any deflection adjustment of the line of sight may be effected by pushing up on nut 8'! to separate teeth 82 from 85, turning member 89 to the nearest ZOO-mil unit next below the angular adjustment desired, releasing unit 3'! to permit the teeth to re-engage, under the urge of spring 86. The adjustment is then completed by turning of skirt 96 to effect translation of contact and turning of member 89. The total deflection setting is then the sum of the two readings. The normal position wherein the line of sight of collimater 01 is parallel to the plane of fire, corresponding to a setting of 3300 mils, namely, 3200 on the scale carried by head 69, and 100 on the micrometer. Readings above 3300 mils correspond to left deflections of the line of sight while readings below 3300 mils corresponds to right deflections.

The collimator 91 may be of any approved type such as the one shown in Figure 1. It is held by a screw 98 within a channel formed diametrically in a circular head 99. This head has an integral shank I00 journaled within a hole in member 89, and having a reduced threaded end engaged by a nut I 0 I. A spring washer I02 provides the necessary friction to hold head 99 in adjusted position relatively to 89. From Figure it will be noted that an open sight for rough sighting, is provided in the form of a notch or groove I00, extending adjacent the longitudinal level 80. The use and operation of this modification is substantially the same as that described in connections with Figures l to 8, inclusive, so that it is deemed unnecessary to repeat. If desired, a lever similar to 52, Figure 3, may be provided, pivoted upon head 69, and having one end in engagement with the end of shaft 88 so that the teeth 32 and 85 may be moved out of engagement by pressure applied to the other end of the lever.

In Figure 13 is shown a further modification which has the advantage that the toothed elements are substantially enclosed. A portion of the lower deflection head or base is indicated at I01, and comprises an upstanding ring I03, open at its top and provided with an indicating opening I I6 having an indicator mark on one beveled wall. A pivot screw I 09 is threaded into head I0! to extend coaxially of ring I08 and has a reduced shank.

An annular detent member I I0 fits within ring I03 and is secured therein by a number of radially-extending screws, one of which is shown at III. Member H0 has its lower surface formed with teeth spaced regularly to define steps of 200 mils each about the axis of screw I08. It will be noted that a flange on member H0 fits over the end of ring I03 to form therewith a dust-tight joint.

The upper deflection head includes a spool H2 having a re-entrant core rotatable and axially slidable on the reduced shank of screw I09 and providing a chamber, annular in cross-section, to accommodate a compression coil spring H3. A second detent member H4 fits within ring I08 and is secured to spool I I2, by a number of screws, one of which is shown at H5. Member H4 has its upper annular end formed with a series of teeth similar to those of member H0. The two series of teeth are urged into intermeshing relation by spring H3 in the same manner and for the same purpose as 4|, 48, Figures 3 and 4, and 60 and 83, Figures 9 and 10. In addition, the upper flange of spool H2 has a smooth sliding and rotatable fit within ring-shaped detent member H0. A mil scale, similar to that shown at Figure 7, is formed upon the periphery of member H4 and coacts with the aforementioned indicator on the wall of opening H6, to give the relative angular adjustment between the two detent members. The elevation head II'! of the sight shown in Figure 13 is indicated in dotted lines and may be identical in construction with the one disclosed in Figure 2. Thus, fine adjustment is effected in the same manner as in Figures 1 and 2, that is, by rotation of a worm journaled in the elevation head and engaging the eccentric extension H8 formed on the end of a pin H9, and locked in adjusted position by a screw I20. Pin H9 may be a duplicate of pin 26, Figure l.

A bracket I 2 I, generally in the form of a channel section, is fixed to the upper surface of spool H2, and has a pivot screw I22 threaded into an aperture in one side. The screw has smooth shank portions of two different diameters and the collimator support I23 has a counterbore hole by which the support is journaled upon the pin. The counterbore is of suflicient depth to receive a coil spring I24 surrounding the reduced shank of pin I22 and acting to urge the support to the left as seen in Figure 13. The left side of bracket I2I is provided with a forked projection I25 between which the edge of support I23 fits smoothly and without play, when the parts are in the position shown, to thereby hold the support in erect position. By translation of support I23 to the right along pin I22 against the action of spring I2 5, it may be freed from projection I25 and rotated downwardly into collapsed position substantially at right angles to the position shown. Another projection, not shown, similar to I25, may be provided upon bracket I2 I to maintain the support in collapsed position.

The collimator I26 is carried by a bracket I33 pivoted on support I23 by a bolt I21 having its axis at right angles to that of screw I22, to provide for the same adjustment as that afforded by bolt 33, Figure 1, and I00, Figure 10. The support I23 is formed with hinge joint sections I28 and I29, between a section I30 of a support for a back sight mirror I3I journaled, as by means of hinge bolt I32. Thus, by rotating mirror I3I through upwardly out of the plane of paper, Figure 13, and then rotating both support, mirror and collimator through 90 upwardly out of the plane of the paper of said figure, the sight may be collapsed into a small compact space for packing and storage in its case. From Figure 14, it will be noted that the collimator bracket I33 is generally in the shape of an inverted U receiving support I23 therebetween with a smooth fit, and that it carries at one side a projection I34 on which the collimator proper I26 is fixed. The collimator itself comprises the unusual optical and open sights, mounted in side-by-side relation. In this figure, the mirror I 3| is shown pivoted into operative back-sighting posiiton about the axis bolt I32. In adjusting the form of sight in deflection, it is sufficient simply to press downwardly upon bracket IZI to thereby move detent member H4 out of contact with H0, then turn the bracket until the next lowest ZOO-mil unit of the desired adjustment as indicated upon the scale on member H4, appears opposite the indicator on the wall of ring I08 adjacent opening I I0. The bracket is then released and spring I I3 acts to move the teeth again into locking engagement. Thereupon, the knob, not shown, but corresponding to 3I, Figure 2, is turned to rotate the deflection head and parts carried thereby through the remaining fraction of the 200-mil unit necessary to effect the desired adjustment.

There is thus provided a mortar sight that is rotatable in deflection in a highly accurate manner, to any position in azimuth whereby the most advantageous aiming point for each tactical situation may be selected. Adjustment is rapid, easy of operation, and may be efiected with one hand. Numerous alterations, modifications and substitutions will be obvious or readily occur to those skilled in the art and hence I do not wish to be limited to the precise constructions shown. To the contrary, it is my intention that the foregoing disclosure shall be taken in an illustrative, rather than a limiting sense, and to reserve all such changes as fall within the scope of the subjoined claims.

Having now fully disclosed the invention, what I claim and desire to secure by Letters Patent is:

1. In a mortar sight, alga clget adapfl fiato be detachably mountednponea lmortarfai'i' elevation head mounted upon said bracket for pivotal movement thereon about a normally horizontal axis, normally vertical pivot means carried by said elevation head and defining a deflection axis, a lower detent member having a first series of equally spaced teeth, said lower detent member being carried by said elevation head and havin its teeth extending through 360 concentric of said deflection axis, an upper detent member mounted on said lower detent member for pivotal movement about said deflection axis, a second series of teeth on said upper detent member and extending through 360 about said deflection axis and adapted to mesh with said first series of teeth, means yieldingly urging said members into interengagement to thereby cause said teeth to intermesh, a collimatorgmounted on said upper detent member for pivotal movement about a normally horizontal axis perpendicular to the line of sight determined by said collimatgr and means pivoted on said lower detent member and manually operable to move said upper detent member axially away from said lower detent member to separate the teeth thereof.

2. For use with a mortar sight having a deflection head pivoted on an elevation head for limited angular movement about a first normally vertical axis, an attachment comprising a lower detent member including a pair of depending spaced parallel arms and a series of upstanding, regularly-spaced teeth extending 360 in a circular path about said first axis, an upper detent member having a like series of depending regularly-spaced teeth adapted to intermesh with the teeth of said lower detent member, a headed pivot screwthreaded into said upper detent member along said first axis and slidably fitting an axial aperture in said lower detent member, a coil spring interposed between the head of said pivot screw and said lower detent member to urge the teeth of said members into mesh, a.lever pivoted between said arms and operable to engage the head of said screw to move said upper detent member axially to separate said teeth against the action 0f said spring, and a collimator sight mounted on said upper detent member for pivotal movement about a normally horizontal axis at right angles to the line of sight determined thereby.

GEORGE L. HERTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 716,114 Schneider et a1. Dec. 16, 1902 1,939,540 Charvet Dec. 12, 1933 2,010,397 Joyce Aug. 6, 1935 2,032,366 Karnes Mar. 3, 1936 2,491,476 Brown Dec. 20, 1949 

